# std::chrono::time_point_cast

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< cpp‎ | chrono‎ | time point

Defined in header `<chrono>` |  |
template< class ToDuration, class Clock, class Duration > std::chrono::time_point<Clock, ToDuration> time_point_cast( const std::chrono::time_point<Clock, Duration> &t ); |  | (since C++11) (until C++14)
template< class ToDuration, class Clock, class Duration > constexpr std::chrono::time_point<Clock, ToDuration> time_point_cast( const std::chrono::time_point<Clock, Duration> &t ); |  | (since C++14)

Converts a std::chrono::time_point from one duration to another.

`time_point_cast` participates in overload resolution only if `ToDuration` is a specialization of std::chrono::duration.

### Parameters

t | - | `time_point` to convert from

### Return value

std::chrono::time_point<Clock, ToDuration>(
std::chrono::duration_cast<ToDuration>(t.time_since_epoch())).

### Example

Run this code

    #include <chrono>
    #include <iostream>
    using namespace std::chrono_literals;

    using Clock = std::chrono::high_resolution_clock;
    using Ms = std::chrono::milliseconds;
    using Sec = std::chrono::seconds;

    template<class Duration>
    using TimePoint = std::chrono::time_point<Clock, Duration>;

    inline void print_ms(const TimePoint<Ms>& time_point)
    {
        std::cout << time_point.time_since_epoch().count() << " ms\n";
    }

    int main()
    {
        TimePoint<Sec> time_point_sec{4s};

        // implicit conversion, no precision loss
        TimePoint<Ms> time_point_ms = time_point_sec;
        print_ms(time_point_ms); // 4000 ms

        time_point_ms = TimePoint<Ms>{5756ms};
        print_ms(time_point_ms); // 5756 ms

        // explicit cast, need when precision loss may happen
        // 5756 truncated to 5000
        time_point_sec = std::chrono::time_point_cast<Sec>(time_point_ms);
        print_ms(time_point_sec); // 5000 ms
    }

Output:

    4000 ms
    5756 ms
    5000 ms

### See also

floor(std::chrono::time_point) (C++17) | converts a time_point to another, rounding down (function template)
ceil(std::chrono::time_point) (C++17) | converts a time_point to another, rounding up (function template)
round(std::chrono::time_point) (C++17) | converts a time_point to another, rounding to nearest, ties to even (function template)
duration_cast (C++11) | converts a duration to another, with a different tick interval (function template)

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